This project is part of stream 3 of the THRESHOLDS project (see parent project). A conceptual planktonic network for food-web bifurcations is proposed, based on partner expertise in different semi-enclosed seas (Black Sea, North Sea, Baltic Sea) and targeted mesocosm experiments with different nutrient conditions. This conceptual model of food-web interactions constitutes the basic frame for identifying the data needs for ecosystem analysis and the subsequent identification of nutrient thresholds for planktonic food-web disruptions.